1. Field of the Invention
The present invention relates to seats for tractors and other off-road vehicles which encounter substantial amounts of vibration and other motion, and more particularly to seats for such vehicles which are capable of undergoing attenuating movement in response to the vibration and other motion.
2. History of the Prior Art
Off-road vehicles such as agricultural tractors and similar vehicles subject the rider to a substantial amount of vibration and other motion due to the nature of the vehicle itself and particularly to the roughness and unevenness of terrain typically negotiated by such vehicles. Consequently, it is common to provide the seats in such vehicles with the ability to undergo limited attenuating movement in one or more directions to compensate for such vibrations and other motion. Many early tractor seats, for example, were constructed so as to be capable of undergoing some vertical movement. This movement was typically controlled using damping pistons and similar apparatus. Later tractor seats came to be provided with attenuating horizontal movement in addition to or in lieu of attenuating vertical movement.
An example of a seat for use with tractors and similar off-road vehicles which is capable of attenuating movement in a generally horizontal direction is provided by a co-pending application Ser. No. 960,125, filed Nov. 13, 1978 and assigned to the assignee of the present application. The seat described in that patent application is capable of attenuating fore-aft motion by an underseat arrangement which includes a plurality of bearings slidable along parallel bars. The seat is retained in a nominal position by an opposing pair of springs, and motion of the seat is damped by a piston.
Further examples of prior art seat arrangements which provide attenuating fore-aft movement are provided by U.S. Pat. No. 3,258,241 of Oswald, U.S. Pat. No. 3,100,617 of Radke et al. and U.S. Pat. No. 2,932,342 of Simons et al. Shock absorption of seat movement in the fore-aft direction is described in U.S. Pat. No. 3,190,592 of Grizzle, Jr. and U.S. Pat. No. 3,100,618 of Tengler et al.
Still other examples of prior art seat arrangements permitting limited our attenuating movement are provided by U.S. Pat. Nos. 3,245,486 of Oswald, 3,335,996 of Hall et al, 3,061,260 of Simons et al, 3,999,800 of Penzotti, 4,099,777 of Chekirda, 3,917,210 of Miller, 4,195,883 of Ronnhult et al, 4,128,217 of Mazelsky, French Pat. No. 742,189 of Fricard and British Patent Specification No. 1,303,936 ofNystrom.
The prior art seat arrangements previously described typically limit attenuating movement in a horizontal plane or direction to a single axis or direction of movement. Based on the types of motion typically encountered by the vehicle the direction may be fore-aft or lateral. As a practical matter the vibrations and other motions encountered occur in all directions, even though they may be more severe in one direction such as fore-aft than in an opposite direction.
It would therefore be desirable to provide a seat capable of undergoing attenuating movement along more than one axis within a generally horizontal plane. Ideally, the seat should be capable of attenuating movement in any and all directions within a generally horizontal plane.